How to Build A Tornado Shelter: Construction Tips on Storm Cellar for the Entire Family

Tornadoes are a very common phenomenon in the United States and almost every year thousands of people suffer from its consequences. In such circumstances building a tornado shelter no longer seems like a weird thing to do and plan. More and more families spend time and resources preparing a special shelter or safe room to be able to protect their family and themselves. It is a time-consuming task, but it’s worth it.

There are many things to consider before you actually start building the shelter. In fact, you’ll have to spend equal time gathering material and information, and building the actual shelter. The more time you spend on the research and consultation with professionals, the better you’ll be prepared when the actual building begins. We also highly advise you to consult with the FEMA documentation, found on their website.

The ‘Taking shelter from the storm’ is a booklet you must be acquainted with before you start building and gathering material. Not only that, but FEMA has set some strict regulations about the requirements for building a shelter. You can find these requirements again in the document mentioned above, the so-called FEMA 320.

Start the preparation for building the shelter

The next most important thing, after you’ve read the FEMA requirements, you have to obtain a construction permit. The National Performance Criteria for Tornado Shelters has set some criteria you absolutely must follow to ensure the shelter provides full security and protection.

This means that you’ll need this permit, including advice from a professional builder or architect. They have to inspect the area, soil and conditions in order to determine how the shelter can be built for optimal protection. In case you want to use the FEMA 320 guidelines, your plans need to be first approved by the National Performance Criteria.

Moving on, you need to also assess the wind zone. This means that you have to determine the wind’s direction. There are usual currents and you have to determine from which direction the wind (and potentially a tornado) would come. This will be a good guideline about how sturdy and reliable the shelter must be built. So, you can check a wind zone map in order to determine these details. FEMA also provide useful information in this regard.

Next you have to determine and decide where to build the shelter. Should it be in the basement, inside the house, attached to the house or should it be a completely separate building in your backyard? The decision you make may be based on your financial status or your personal preference. Usually tornado shelters built under the house may require some retrofitting of the house and may be more costly. If you want to build a shelter, without changing the house’s construction, this may be the cheapest way.

Building a separate construction some 150 feet from the house (no further than 150 feet) can also be a more economical approach. The only problem is that you would be exposed to potentially strong winds, which may endanger your life, as you try to reach the outside shelter. That’s why is important to learn about safety regulations while battling a tornado, like the ones we described here.

An attachment to the house is also a great way to cheaply and economically build a tornado shelter.

Building process

To begin with, you need to first gather your material. You need metal frames, lots of concrete for building the walls, roof and floor, and various tools for the actual building.

Start off with digging the hole first. You’ll need to dig it a bit larger than initially planned, so that you have room enough to maneuver inside the hole. Also, consider that a tornado shelter doesn’t have to be large (like a storm shelter), since tornadoes don’t last long and you can spend an hour or so inside, without access to bathroom, kitchen, etc. Of course, building a tornado shelter means you have to prepare some room for safety and emergency kits, including a first-aid kit; they are a-must in case anyone got injured.

So, to measure the shelter, you can count 3 square feet per person. Judging by this you can determine the size of the entire shelter. Count another 1 square foot for the emergency kits and you’ll have the total size for the shelter. Use the FEMA documentation and design plans for determining how to use the given space in an optimal way.

Before you start building and laying the floor you have to first drill holes through the ground floor of your house. As you prepare the floor, and you lay the concrete shelter floor, keep bolts into the floor. Ideally, you may have to make anchors separately first. Make them using metal frame and pouring concrete into blocks to keep the anchors stable and solid. Then you can attach the shelter floor to it. Otherwise, proceed to laying the floor.

You need to use concrete for the floor and you need to make it thick, about 5 inches at least, so that it holds firmly in place. If you’re building the shelter immediately in contact with soil, you’ll have to first level the ground, before you pour the concrete. If you’re building inside your house, you don’t have to do that, since the floor is already flat. If the tornado shelter is meant as an outside attachment to the house, then you’ll also have to be sure to level the ground before you continue building.

You’re ready to pour the concrete. The amount must be calculated properly according to the overall size for the shelter and by taking into account that the thickness should be about 5 inches. As you’ve done that, lay the floor and wait for it to dry. This may take up to a week.

During that time, it’s advisable (but not crucial) to pour water over the drying concrete and always keep it wet. This will protect the concrete from cracking during the drying process and many professionals use this practice in their work. And since concrete is like a sponge, it absorbs a lot of water and moisture, so you’ll have to keep it wet almost all the time. Make sure, if you’re building inside your house, to keep the room well ventilated so that no mold gathers. If that happens, wash it and repaint the walls or roof where it gathered.

Your next step is to prepare the walls (which are the bulk of your work). You need to make them strong enough so that they can withstand winds of up to 250mph (and even more). The walls need to have a very sturdy frame. Most tornado shelters have metal bars as a frame, as it can withstand incredible pressure. Fiberglass or wood board are also options, but the latter may be less durable, so you have to plan well what material to use. It all depends on what wind zone you’re located at, so you have to take that into consideration.

As the frame is set and ready, it’s time to start arranging the concrete blocks and build the walls. You will need a hammer drill to make holes on each concrete block, so that the frame you set can go through the blocks. This gives more stability to the entire construction. Begin by laying the first layer of blocks. You will have to arrange them in an intersecting pattern, so that each two blocks hold one another on top of them. It’s a pattern regularly used when building structures, houses, etc.

As you made the first concrete blocks layer, pour concrete in the blocks’ holes. By doing so, the new concrete will strengthen the link between the frame and the blocks and will make the base solid and virtually immovable. Again, keep in mind that if you don’t want cracks in the new poured concrete, you may want to keep it wet and water it as it cures.

Keep arranging the next level of concrete bricks and repeat the process every time you finish a level. Determine the height of the entire shelter – it should be taller than the tallest member of your family. This means more than 7-8 feet. As you’ve reached this relative height you’ll have to determine how to finish the edge. Since it must meet nicely and securely the roof (which you’ll build later), you’ll have to build the edge separately. You’ll attach it later to the shelter.

So, lay your material to the side. You need again concrete bricks, metal frame (or fiberglass) and concrete for pouring. You need to thread through all the bricks the metal frame, so it will go perpendicular to your shelter’s frame. Drill holes through the bricks so that you have the empty space of the bricks facing up (you may have to break some of the compartments in each brick to have one large empty space).

Make this entire thing, so that it can fit perfectly with the edge of your shelter. Put more metal bars into the holes, so that they stick out of the bricks and are parallel to the walls’ frame. You’ll see why later.

As you finished with that, pour concrete into the empty holes of the bricks and again soak the concrete with water as it cures.

As this is done and the concrete is ready, you have to lay this top edge over the shelter. Now it’s time to attach the top edge you just made to the shelter’s edge. Thread the metal bars of the walls through the top edge and you’re done with that. The metal bars that are sticking out of the edge must be bent so that you can then attach and fuse more metal bars. Do so, and make this further installation so that the metal bars are crossing each other like a chess board.

When this step is over, build a wooden frame around it and make it across the entire roof. You will have to pour concrete on top of it to finish with the roof. Drill some holes into the wooden frame so that there is some ventilation going on. Since this is a tornado shelter you won’t spend much time inside this shelter and ventilation isn’t much of a concern. Of course, in case the door is blocked by debris and you can’t leave the shelter after a tornado, you may have to stay inside until rescue team finds you. Until then, you will have to stay inside.

So, ventilation is important and don’t forget to make sure that there will be sufficient amount of fresh air coming in. This is especially true if you have a large family – it can get stuffed inside very quickly, since you’re building a very small safe room.

Finally, you have to attach the door to the shelter. It has to be special and can’t be any type e of door. You’re highly advised to purchase a special door exactly for your purposes. There are doors specifically made for tornado shelters and are tested and certified by FEMA. Before you commit to a purchase, look for labels and seals certifying these tests.

Usually these special doors are sold directly with hinges, which are tested alongside the doors themselves. FEMA advises you never to use other hinges for doors they have approved, since they can’t guarantee that these hinges will provide enough security, and may in fact even cause injuries and compromise your safety.

This approach explained above can be applied in a similar fashion to a basement in your house. You can begin laying the foundations, anchors, walls and roof in the same way. You could also build the shelter within the basement’s construction, but that may not be as economical. In any case, basements are much safer than the house itself, since it is build under the ground. That gives protection from the tornado, but not full cover, as the wind can be so strong as to destroy the house’s floor and compromise your safety in the basement.

So building a shelter room inside the basement may be the best idea, as it provides a second layer of protection. Usually tornado shelters are made (as explained above) using lots of heavy materials, and the sheer weight of the tornado shelter can be almost enough to keep it stuck solidly and firmly to the ground.

Further advice

You can also get some advice from professional builders for these instructions and ask them to help you with your shelter. In this way you’ll be sure that the construction will definitely sustain heavy pressure from wind, falling and flying debris, etc.

Also, keep in mind that if you follow the above instructions and you feel like you’re unsure about some of the steps, or you have to substitute some materials for others, then it’s best to consult specialists and professionals. After all, the tornado shelter will be a safe protection only if all the parts are installed and build properly. If not, even a wrong hinge may endanger the people inside.

A good idea is to build a safe room in the house. This way, you won’t have to leave the house and you don’t risk being buried under the house if everything goes wrong. If you want to know more, we have a detailed article on tornado safe rooms you should check out.

Another advice is not to build any windows, openings, etc. since they lessen the strength of the construction. The only opening should be for the door. As long as the door is specifically tested for tornado conditions, you’re more or less safe inside the shelter.

Also, don’t build a shelter below ground level if you’re in a flood area or near the coast, as water may flood the basement and you won’t be able to escape. If that is the case, build the shelter above the ground and keep the anchors of the shelter built inside the ground. You may have to do some retrofitting to your house. If you’re currently building your house and plan on adding a tornado shelter, then build it while you’re building the house – it’s much less costly and will give additional strength to the house’s construction and foundations.

If your area is prone to storms and tornadoes you may want to just build a storm shelter, as it can be used for both storms (hurricanes) and tornadoes. If hurricanes are not a concern, you may want to build a very small shelter. It doesn’t even have to be as tall as an adult person. Some people build shelters as small as bomb shelters, just so they can be safe during the tornado. After all these last only for a short period of time and comfort isn’t exactly a top priority.

If you decide to build such a small shelter you can also save on money and get to build an economical construction. Usually the most economical shelter may cost you about $500. Larger shelters usually cost several thousand dollars. Building your own shelter may cost you for the materials (and some professional builder’s help and advice) about $2000.

Of course, if you want you can purchase an already made tornado shelter. These are sold at much affordable prices and can be attached to your existing house. They are fully equipped with a door with hinges and some even come with emergency and first-aid kits. Again, if you purchase a pre-made shelter, don’t change any of its elements – they are specifically used together to provide the highest safety.

About the Author

David Dawson

David Dawson is a retired security specialist with over 20 years of experience. He worked for a secret manufacturing facilities and hospitals in Illinois. David's responsibility was to protect people in case of any disaster or cataclysm that might occur. Now he keeps on doing it through teaching others about how to prepare and survive flood, earthquake or even war.

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